From: Jan Beulich Date: Tue, 6 Mar 2018 15:49:36 +0000 (+0100) Subject: x86: remove CR reads from exit-to-guest path X-Git-Tag: archive/raspbian/4.11.1-1+rpi1~1^2~66^2~463 X-Git-Url: https://dgit.raspbian.org/%22http://www.example.com/cgi/%22/%22http:/www.example.com/cgi/%22?a=commitdiff_plain;h=31bf55cb5fe3796cf6a4efbcfc0a9418bb1c783f;p=xen.git x86: remove CR reads from exit-to-guest path CR3 is - during normal operation - only ever loaded from v->arch.cr3, so there's no need to read the actual control register. For CR4 we can generally use the cached value on all synchronous entry end exit paths. Drop the write_cr3 macro, as the two use sites are probably easier to follow without its use. Signed-off-by: Jan Beulich Tested-by: Juergen Gross Reviewed-by: Juergen Gross Reviewed-by: Andrew Cooper --- diff --git a/xen/arch/x86/x86_64/asm-offsets.c b/xen/arch/x86/x86_64/asm-offsets.c index 1a4542812c..a2fea94f4c 100644 --- a/xen/arch/x86/x86_64/asm-offsets.c +++ b/xen/arch/x86/x86_64/asm-offsets.c @@ -87,6 +87,7 @@ void __dummy__(void) OFFSET(VCPU_kernel_ss, struct vcpu, arch.pv_vcpu.kernel_ss); OFFSET(VCPU_iopl, struct vcpu, arch.pv_vcpu.iopl); OFFSET(VCPU_guest_context_flags, struct vcpu, arch.vgc_flags); + OFFSET(VCPU_cr3, struct vcpu, arch.cr3); OFFSET(VCPU_arch_msr, struct vcpu, arch.msr); OFFSET(VCPU_nmi_pending, struct vcpu, nmi_pending); OFFSET(VCPU_mce_pending, struct vcpu, mce_pending); diff --git a/xen/arch/x86/x86_64/entry.S b/xen/arch/x86/x86_64/entry.S index cc5b95e5c1..64937969f5 100644 --- a/xen/arch/x86/x86_64/entry.S +++ b/xen/arch/x86/x86_64/entry.S @@ -45,7 +45,7 @@ restore_all_guest: mov VCPUMSR_spec_ctrl_raw(%rdx), %r15d /* Copy guest mappings and switch to per-CPU root page table. */ - mov %cr3, %r9 + mov VCPU_cr3(%rbx), %r9 GET_STACK_END(dx) mov STACK_CPUINFO_FIELD(pv_cr3)(%rdx), %rdi movabs $PADDR_MASK & PAGE_MASK, %rsi @@ -67,8 +67,13 @@ restore_all_guest: sub $(ROOT_PAGETABLE_FIRST_XEN_SLOT - \ ROOT_PAGETABLE_LAST_XEN_SLOT - 1) * 8, %rdi rep movsq + mov STACK_CPUINFO_FIELD(cr4)(%rdx), %rdi mov %r9, STACK_CPUINFO_FIELD(xen_cr3)(%rdx) - write_cr3 rax, rdi, rsi + mov %rdi, %rsi + and $~X86_CR4_PGE, %rdi + mov %rdi, %cr4 + mov %rax, %cr3 + mov %rsi, %cr4 .Lrag_keep_cr3: /* Restore stashed SPEC_CTRL value. */ @@ -124,7 +129,12 @@ restore_all_xen: * so "g" will have to do. */ UNLIKELY_START(g, exit_cr3) - write_cr3 rax, rdi, rsi + mov %cr4, %rdi + mov %rdi, %rsi + and $~X86_CR4_PGE, %rdi + mov %rdi, %cr4 + mov %rax, %cr3 + mov %rsi, %cr4 UNLIKELY_END(exit_cr3) /* WARNING! `ret`, `call *`, `jmp *` not safe beyond this point. */ diff --git a/xen/include/asm-x86/asm_defns.h b/xen/include/asm-x86/asm_defns.h index 24a269c546..cc5ec65ad2 100644 --- a/xen/include/asm-x86/asm_defns.h +++ b/xen/include/asm-x86/asm_defns.h @@ -208,15 +208,6 @@ void ret_from_intr(void); #define ASM_STAC ASM_AC(STAC) #define ASM_CLAC ASM_AC(CLAC) -.macro write_cr3 val:req, tmp1:req, tmp2:req - mov %cr4, %\tmp1 - mov %\tmp1, %\tmp2 - and $~X86_CR4_PGE, %\tmp1 - mov %\tmp1, %cr4 - mov %\val, %cr3 - mov %\tmp2, %cr4 -.endm - #define CR4_PV32_RESTORE \ 667: ASM_NOP5; \ .pushsection .altinstr_replacement, "ax"; \