From ecb93d1ccd0aac63f03be2db3cac3fa974716f4c Mon Sep 17 00:00:00 2001 From: Jeremy Fitzhardinge Date: Wed, 28 Jan 2009 14:35:05 -0800 Subject: x86/paravirt: add register-saving thunks to reduce caller register pressure Impact: Optimization One of the problems with inserting a pile of C calls where previously there were none is that the register pressure is greatly increased. The C calling convention says that the caller must expect a certain set of registers may be trashed by the callee, and that the callee can use those registers without restriction. This includes the function argument registers, and several others. This patch seeks to alleviate this pressure by introducing wrapper thunks that will do the register saving/restoring, so that the callsite doesn't need to worry about it, but the callee function can be conventional compiler-generated code. In many cases (particularly performance-sensitive cases) the callee will be in assembler anyway, and need not use the compiler's calling convention. Standard calling convention is: arguments return scratch x86-32 eax edx ecx eax ? x86-64 rdi rsi rdx rcx rax r8 r9 r10 r11 The thunk preserves all argument and scratch registers. The return register is not preserved, and is available as a scratch register for unwrapped callee code (and of course the return value). Wrapped function pointers are themselves wrapped in a struct paravirt_callee_save structure, in order to get some warning from the compiler when functions with mismatched calling conventions are used. The most common paravirt ops, both statically and dynamically, are interrupt enable/disable/save/restore, so handle them first. This is particularly easy since their calls are handled specially anyway. XXX Deal with VMI. What's their calling convention? Signed-off-by: H. Peter Anvin --- arch/x86/lguest/boot.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) (limited to 'arch/x86/lguest') diff --git a/arch/x86/lguest/boot.c b/arch/x86/lguest/boot.c index 92f1c6f..19e33b6 100644 --- a/arch/x86/lguest/boot.c +++ b/arch/x86/lguest/boot.c @@ -173,24 +173,29 @@ static unsigned long save_fl(void) { return lguest_data.irq_enabled; } +PV_CALLEE_SAVE_REGS_THUNK(save_fl); /* restore_flags() just sets the flags back to the value given. */ static void restore_fl(unsigned long flags) { lguest_data.irq_enabled = flags; } +PV_CALLEE_SAVE_REGS_THUNK(restore_fl); /* Interrupts go off... */ static void irq_disable(void) { lguest_data.irq_enabled = 0; } +PV_CALLEE_SAVE_REGS_THUNK(irq_disable); /* Interrupts go on... */ static void irq_enable(void) { lguest_data.irq_enabled = X86_EFLAGS_IF; } +PV_CALLEE_SAVE_REGS_THUNK(irq_enable); + /*:*/ /*M:003 Note that we don't check for outstanding interrupts when we re-enable * them (or when we unmask an interrupt). This seems to work for the moment, @@ -984,10 +989,10 @@ __init void lguest_init(void) /* interrupt-related operations */ pv_irq_ops.init_IRQ = lguest_init_IRQ; - pv_irq_ops.save_fl = save_fl; - pv_irq_ops.restore_fl = restore_fl; - pv_irq_ops.irq_disable = irq_disable; - pv_irq_ops.irq_enable = irq_enable; + pv_irq_ops.save_fl = PV_CALLEE_SAVE(save_fl); + pv_irq_ops.restore_fl = PV_CALLEE_SAVE(restore_fl); + pv_irq_ops.irq_disable = PV_CALLEE_SAVE(irq_disable); + pv_irq_ops.irq_enable = PV_CALLEE_SAVE(irq_enable); pv_irq_ops.safe_halt = lguest_safe_halt; /* init-time operations */ -- cgit v1.1 From ccbeed3a05908d201b47b6c3dd1a373138bba566 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Mon, 9 Feb 2009 22:17:40 +0900 Subject: x86: make lazy %gs optional on x86_32 Impact: pt_regs changed, lazy gs handling made optional, add slight overhead to SAVE_ALL, simplifies error_code path a bit On x86_32, %gs hasn't been used by kernel and handled lazily. pt_regs doesn't have place for it and gs is saved/loaded only when necessary. In preparation for stack protector support, this patch makes lazy %gs handling optional by doing the followings. * Add CONFIG_X86_32_LAZY_GS and place for gs in pt_regs. * Save and restore %gs along with other registers in entry_32.S unless LAZY_GS. Note that this unfortunately adds "pushl $0" on SAVE_ALL even when LAZY_GS. However, it adds no overhead to common exit path and simplifies entry path with error code. * Define different user_gs accessors depending on LAZY_GS and add lazy_save_gs() and lazy_load_gs() which are noop if !LAZY_GS. The lazy_*_gs() ops are used to save, load and clear %gs lazily. * Define ELF_CORE_COPY_KERNEL_REGS() which always read %gs directly. xen and lguest changes need to be verified. Signed-off-by: Tejun Heo Cc: Jeremy Fitzhardinge Cc: Rusty Russell Signed-off-by: Ingo Molnar --- arch/x86/lguest/boot.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'arch/x86/lguest') diff --git a/arch/x86/lguest/boot.c b/arch/x86/lguest/boot.c index 19e33b6..da2e314 100644 --- a/arch/x86/lguest/boot.c +++ b/arch/x86/lguest/boot.c @@ -283,7 +283,7 @@ static void lguest_load_tls(struct thread_struct *t, unsigned int cpu) /* There's one problem which normal hardware doesn't have: the Host * can't handle us removing entries we're currently using. So we clear * the GS register here: if it's needed it'll be reloaded anyway. */ - loadsegment(gs, 0); + lazy_load_gs(0); lazy_hcall(LHCALL_LOAD_TLS, __pa(&t->tls_array), cpu, 0); } -- cgit v1.1 From c1eeb2de41d7015678bdd412b48a5f071b84e29a Mon Sep 17 00:00:00 2001 From: Yinghai Lu Date: Mon, 16 Feb 2009 23:02:14 -0800 Subject: x86: fold apic_ops into genapic Impact: cleanup make it simpler, don't need have one extra struct. v2: fix the sgi_uv build Signed-off-by: Yinghai Lu Cc: Andrew Morton Signed-off-by: Ingo Molnar --- arch/x86/lguest/boot.c | 19 ++++++++++--------- 1 file changed, 10 insertions(+), 9 deletions(-) (limited to 'arch/x86/lguest') diff --git a/arch/x86/lguest/boot.c b/arch/x86/lguest/boot.c index da2e314..bc9893f 100644 --- a/arch/x86/lguest/boot.c +++ b/arch/x86/lguest/boot.c @@ -55,7 +55,7 @@ #include #include #include -#include +#include #include #include #include @@ -828,13 +828,14 @@ static u32 lguest_apic_safe_wait_icr_idle(void) return 0; } -static struct apic_ops lguest_basic_apic_ops = { - .read = lguest_apic_read, - .write = lguest_apic_write, - .icr_read = lguest_apic_icr_read, - .icr_write = lguest_apic_icr_write, - .wait_icr_idle = lguest_apic_wait_icr_idle, - .safe_wait_icr_idle = lguest_apic_safe_wait_icr_idle, +static void set_lguest_basic_apic_ops(void) +{ + apic->read = lguest_apic_read; + apic->write = lguest_apic_write; + apic->icr_read = lguest_apic_icr_read; + apic->icr_write = lguest_apic_icr_write; + apic->wait_icr_idle = lguest_apic_wait_icr_idle; + apic->safe_wait_icr_idle = lguest_apic_safe_wait_icr_idle; }; #endif @@ -1035,7 +1036,7 @@ __init void lguest_init(void) #ifdef CONFIG_X86_LOCAL_APIC /* apic read/write intercepts */ - apic_ops = &lguest_basic_apic_ops; + set_lguest_basic_apic_ops(); #endif /* time operations */ -- cgit v1.1 From 7b6aa335ca1a845c2262ec7a595b4521bca0f79d Mon Sep 17 00:00:00 2001 From: Ingo Molnar Date: Tue, 17 Feb 2009 13:58:15 +0100 Subject: x86, apic: remove genapic.h Impact: cleanup Remove genapic.h and remove all references to it. Signed-off-by: Ingo Molnar --- arch/x86/lguest/boot.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'arch/x86/lguest') diff --git a/arch/x86/lguest/boot.c b/arch/x86/lguest/boot.c index bc9893f..f3a5305 100644 --- a/arch/x86/lguest/boot.c +++ b/arch/x86/lguest/boot.c @@ -55,7 +55,7 @@ #include #include #include -#include +#include #include #include #include -- cgit v1.1 From 965c7ecaf2e2b083d711a01ab33735a4bdeee1a4 Mon Sep 17 00:00:00 2001 From: Ingo Molnar Date: Sun, 22 Feb 2009 23:19:12 +0100 Subject: x86: remove the Voyager 32-bit subarch Impact: remove unused/broken code The Voyager subarch last built successfully on the v2.6.26 kernel and has been stale since then and does not build on the v2.6.27, v2.6.28 and v2.6.29-rc5 kernels. No actual users beyond the maintainer reported this breakage. Patches were sent and most of the fixes were accepted but the discussion around how to do a few remaining issues cleanly fizzled out with no resolution and the code remained broken. In the v2.6.30 x86 tree development cycle 32-bit subarch support has been reworked and removed - and the Voyager code, beyond the build problems already known, needs serious and significant changes and probably a rewrite to support it. CONFIG_X86_VOYAGER has been marked BROKEN then. The maintainer has been notified but no patches have been sent so far to fix it. While all other subarchs have been converted to the new scheme, voyager is still broken. We'd prefer to receive patches which clean up the current situation in a constructive way, but even in case of removal there is no obstacle to add that support back after the issues have been sorted out in a mutually acceptable fashion. So remove this inactive code for now. Signed-off-by: Ingo Molnar --- arch/x86/lguest/Kconfig | 1 - 1 file changed, 1 deletion(-) (limited to 'arch/x86/lguest') diff --git a/arch/x86/lguest/Kconfig b/arch/x86/lguest/Kconfig index c70e12b..8dab8f7 100644 --- a/arch/x86/lguest/Kconfig +++ b/arch/x86/lguest/Kconfig @@ -3,7 +3,6 @@ config LGUEST_GUEST select PARAVIRT depends on X86_32 depends on !X86_PAE - depends on !X86_VOYAGER select VIRTIO select VIRTIO_RING select VIRTIO_CONSOLE -- cgit v1.1