[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [xen staging] xen/wait: Minor asm improvements
commit 660d69cd5a3714777252d7b804f82e8b7a8a8313 Author: Andrew Cooper <andrew.cooper3@xxxxxxxxxx> AuthorDate: Fri Jul 15 12:27:08 2022 +0100 Commit: Andrew Cooper <andrew.cooper3@xxxxxxxxxx> CommitDate: Mon Jul 18 15:55:53 2022 +0100 xen/wait: Minor asm improvements There is no point preserving all registers. Instead, preserve an arbitrary 6 registers, and list the rest as clobbered. This does not alter the register scheduling at all, but does reduce the amount of state needing saving. Use a named parameter for page size, instead of needing to parse which is parameter 3. Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx> Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx> --- xen/common/wait.c | 33 +++++++++++++++++---------------- 1 file changed, 17 insertions(+), 16 deletions(-) diff --git a/xen/common/wait.c b/xen/common/wait.c index 1f0285ac30..e45345ede7 100644 --- a/xen/common/wait.c +++ b/xen/common/wait.c @@ -151,13 +151,12 @@ static void __prepare_to_wait(struct waitqueue_vcpu *wqv) * copies in from wqv->stack over the active stack. */ asm volatile ( - "push %%rax; push %%rbx; push %%rdx; push %%rbp;" - "push %%r8; push %%r9; push %%r10; push %%r11;" - "push %%r12; push %%r13; push %%r14; push %%r15;" + "push %%rbx; push %%rbp; push %%r12;" + "push %%r13; push %%r14; push %%r15;" "sub %%esp,%%ecx;" - "cmp %3,%%ecx;" - "ja .L_skip;" + "cmp %[sz], %%ecx;" + "ja .L_skip;" /* Bail if >4k */ "mov %%rsp,%%rsi;" /* check_wakeup_from_wait() longjmp()'s to this point. */ @@ -165,12 +164,12 @@ static void __prepare_to_wait(struct waitqueue_vcpu *wqv) "mov %%rsp,%%rsi;" ".L_skip:" - "pop %%r15; pop %%r14; pop %%r13; pop %%r12;" - "pop %%r11; pop %%r10; pop %%r9; pop %%r8;" - "pop %%rbp; pop %%rdx; pop %%rbx; pop %%rax" + "pop %%r15; pop %%r14; pop %%r13;" + "pop %%r12; pop %%rbp; pop %%rbx" : "=&S" (wqv->esp), "=&c" (dummy), "=&D" (dummy) - : "i" (PAGE_SIZE), "0" (0), "1" (cpu_info), "2" (wqv->stack) - : "memory" ); + : "0" (0), "1" (cpu_info), "2" (wqv->stack), + [sz] "i" (PAGE_SIZE) + : "memory", "rax", "rdx", "r8", "r9", "r10", "r11" ); if ( unlikely(wqv->esp == 0) ) { @@ -221,13 +220,15 @@ void check_wakeup_from_wait(void) * rep movs in __prepare_to_wait(), it copies from wqv->stack over the * active stack. * - * All other GPRs are available for use; they're restored from the stack. + * All other GPRs are available for use; They're restored from the stack, + * or explicitly clobbered. */ - asm volatile ( - "mov %1,%%"__OP"sp; jmp .L_wq_resume;" - : : "S" (wqv->stack), "D" (wqv->esp), - "c" ((char *)get_cpu_info() - (char *)wqv->esp) - : "memory" ); + asm volatile ( "mov %%rdi, %%rsp;" + "jmp .L_wq_resume" + : + : "S" (wqv->stack), "D" (wqv->esp), + "c" ((char *)get_cpu_info() - (char *)wqv->esp) + : "memory" ); unreachable(); } -- generated by git-patchbot for /home/xen/git/xen.git#staging
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