From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anthony Liguori Subject: [PATCH][SVM] Only save/restore MSRs when needed Date: Fri, 27 Apr 2007 18:30:19 -0500 Message-ID: <4632878B.6090606@us.ibm.com> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="------------070602080103080100010808" To: kvm-devel , Avi Kivity Return-path: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org Errors-To: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org List-Id: kvm.vger.kernel.org This is a multi-part message in MIME format. --------------070602080103080100010808 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit I've tested this with 32-bit and 64-bit guests on a 64-bit host and with 32-bit guests on a 32-bit host. I *think* it's doing the right thing wrt to DEBUGCTL but an extra set of eyes would be helpful. Depending on my machine's mood, we're at somewhere between 3200 and 2700 cycles per VMEXIT. Regards, Anthony Liguori --------------070602080103080100010808 Content-Type: text/x-patch; name="svm-lazy-msrs.diff" Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="svm-lazy-msrs.diff" From: Anthony Liguori Subject: [PATCH][SVM] Only save/restore MSRs when needed We only have to save/restore MSR_GS_BASE on every VMEXIT. The rest can be saved/restored when we leave the VCPU. As a special case, MSR_IA32_DEBUGCTL only needs to be saved/restored on every exit if debugging is enabled in either the host or the guest. Signed-off-by: Anthony Liguori Index: kernel/drivers/kvm/svm.c =================================================================== --- kernel.orig/drivers/kvm/svm.c 2007-04-27 17:52:37.200780944 -0500 +++ kernel/drivers/kvm/svm.c 2007-04-27 18:14:02.098446808 -0500 @@ -611,7 +611,7 @@ static void svm_vcpu_load(struct kvm_vcpu *vcpu) { - int cpu; + int cpu, i; cpu = get_cpu(); if (unlikely(cpu != vcpu->cpu)) { @@ -626,10 +626,24 @@ vcpu->svm->vmcb->control.tsc_offset += delta; vcpu->cpu = cpu; } + + for (i = 0; i < NR_HOST_SAVE_USER_MSRS; i++) + rdmsrl(host_save_user_msrs[i], vcpu->svm->host_user_msrs[i]); + + rdmsrl(MSR_IA32_DEBUGCTLMSR, vcpu->svm->host_ia32_debugctl); } static void svm_vcpu_put(struct kvm_vcpu *vcpu) { + int i; + + for (i = 0; i < NR_HOST_SAVE_USER_MSRS; i++) + wrmsrl(host_save_user_msrs[i], vcpu->svm->host_user_msrs[i]); + + wrmsrl(MSR_IA32_DEBUGCTLMSR, vcpu->svm->host_ia32_debugctl); + /* FIXME: LASTBRANCHFROMIP, LASTBRANCHTOIP, LASTINTFROMIP, + LASTINTTOIP */ + rdtscll(vcpu->host_tsc); put_cpu(); } @@ -815,18 +829,16 @@ static void load_host_msrs(struct kvm_vcpu *vcpu) { - int i; - - for ( i = 0; i < NR_HOST_SAVE_MSRS; i++) - wrmsrl(host_save_msrs[i], vcpu->svm->host_msrs[i]); +#ifdef CONFIG_X86_64 + wrmsrl(MSR_GS_BASE, vcpu->svm->host_gs_base); +#endif } static void save_host_msrs(struct kvm_vcpu *vcpu) { - int i; - - for ( i = 0; i < NR_HOST_SAVE_MSRS; i++) - rdmsrl(host_save_msrs[i], vcpu->svm->host_msrs[i]); +#ifdef CONFIG_X86_64 + rdmsrl(MSR_GS_BASE, vcpu->svm->host_gs_base); +#endif } static void new_asid(struct kvm_vcpu *vcpu, struct svm_cpu_data *svm_data) @@ -1498,6 +1510,11 @@ load_db_regs(vcpu->svm->db_regs); } + if ((vcpu->svm->vmcb->save.dr7 & 0xff) || + (vcpu->svm->host_dr7 & 0xff)) { + wrmsrl(MSR_IA32_DEBUGCTLMSR, vcpu->svm->host_ia32_debugctl); + } + if (vcpu->fpu_active) { fx_save(vcpu->host_fx_image); fx_restore(vcpu->guest_fx_image); @@ -1617,6 +1634,11 @@ fx_restore(vcpu->host_fx_image); } + if ((vcpu->svm->vmcb->save.dr7 & 0xff) || + (vcpu->svm->host_dr7 & 0xff)) { + rdmsrl(MSR_IA32_DEBUGCTLMSR, vcpu->svm->host_ia32_debugctl); + } + if ((vcpu->svm->vmcb->save.dr7 & 0xff)) load_db_regs(vcpu->svm->host_db_regs); Index: kernel/drivers/kvm/kvm_svm.h =================================================================== --- kernel.orig/drivers/kvm/kvm_svm.h 2007-04-27 17:52:37.240774864 -0500 +++ kernel/drivers/kvm/kvm_svm.h 2007-04-27 17:53:42.509852456 -0500 @@ -9,17 +9,15 @@ #include "svm.h" #include "kvm.h" -static const u32 host_save_msrs[] = { +static const u32 host_save_user_msrs[] = { #ifdef CONFIG_X86_64 MSR_STAR, MSR_LSTAR, MSR_CSTAR, MSR_SYSCALL_MASK, MSR_KERNEL_GS_BASE, - MSR_FS_BASE, MSR_GS_BASE, + MSR_FS_BASE, #endif MSR_IA32_SYSENTER_CS, MSR_IA32_SYSENTER_ESP, MSR_IA32_SYSENTER_EIP, - MSR_IA32_DEBUGCTLMSR, /*MSR_IA32_LASTBRANCHFROMIP, - MSR_IA32_LASTBRANCHTOIP, MSR_IA32_LASTINTFROMIP,MSR_IA32_LASTINTTOIP,*/ }; -#define NR_HOST_SAVE_MSRS ARRAY_SIZE(host_save_msrs) +#define NR_HOST_SAVE_USER_MSRS ARRAY_SIZE(host_save_user_msrs) #define NUM_DB_REGS 4 struct vcpu_svm { @@ -32,7 +30,9 @@ u64 next_rip; - u64 host_msrs[NR_HOST_SAVE_MSRS]; + u64 host_user_msrs[NR_HOST_SAVE_USER_MSRS]; + u64 host_ia32_debugctl; + u64 host_gs_base; unsigned long host_cr2; unsigned long host_db_regs[NUM_DB_REGS]; unsigned long host_dr6; --------------070602080103080100010808 Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline ------------------------------------------------------------------------- This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. 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