Messages in this thread | | | Date | Wed, 1 Mar 2023 12:11:57 +0100 | Subject | Re: [RFC PATCH V3 13/16] x86/sev: Add Check of #HV event in path | From | "Gupta, Pankaj" <> |
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On 1/22/2023 3:46 AM, Tianyu Lan wrote: > From: Tianyu Lan <tiala@microsoft.com> > > Add check_hv_pending() and check_hv_pending_after_irq() to > check queued #HV event when irq is disabled. > > Signed-off-by: Tianyu Lan <tiala@microsoft.com> > --- > arch/x86/entry/entry_64.S | 18 +++++++++++++++ > arch/x86/include/asm/irqflags.h | 10 +++++++++ > arch/x86/kernel/sev.c | 39 +++++++++++++++++++++++++++++++++ > 3 files changed, 67 insertions(+) > > diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S > index 6baec7653f19..aec8dc4443d1 100644 > --- a/arch/x86/entry/entry_64.S > +++ b/arch/x86/entry/entry_64.S > @@ -1064,6 +1064,15 @@ SYM_CODE_END(paranoid_entry) > * R15 - old SPEC_CTRL > */ > SYM_CODE_START_LOCAL(paranoid_exit) > +#ifdef CONFIG_AMD_MEM_ENCRYPT > + /* > + * If a #HV was delivered during execution and interrupts were > + * disabled, then check if it can be handled before the iret > + * (which may re-enable interrupts). > + */ > + mov %rsp, %rdi > + call check_hv_pending > +#endif > UNWIND_HINT_REGS > > /* > @@ -1188,6 +1197,15 @@ SYM_CODE_START(error_entry) > SYM_CODE_END(error_entry) > > SYM_CODE_START_LOCAL(error_return) > +#ifdef CONFIG_AMD_MEM_ENCRYPT > + /* > + * If a #HV was delivered during execution and interrupts were > + * disabled, then check if it can be handled before the iret > + * (which may re-enable interrupts). > + */ > + mov %rsp, %rdi > + call check_hv_pending > +#endif > UNWIND_HINT_REGS > DEBUG_ENTRY_ASSERT_IRQS_OFF > testb $3, CS(%rsp) > diff --git a/arch/x86/include/asm/irqflags.h b/arch/x86/include/asm/irqflags.h > index 7793e52d6237..fe46e59168dd 100644 > --- a/arch/x86/include/asm/irqflags.h > +++ b/arch/x86/include/asm/irqflags.h > @@ -14,6 +14,10 @@ > /* > * Interrupt control: > */ > +#ifdef CONFIG_AMD_MEM_ENCRYPT > +void check_hv_pending(struct pt_regs *regs); > +void check_hv_pending_irq_enable(void); > +#endif > > /* Declaration required for gcc < 4.9 to prevent -Werror=missing-prototypes */ > extern inline unsigned long native_save_fl(void); > @@ -43,12 +47,18 @@ static __always_inline void native_irq_disable(void) > static __always_inline void native_irq_enable(void) > { > asm volatile("sti": : :"memory"); > +#ifdef CONFIG_AMD_MEM_ENCRYPT > + check_hv_pending_irq_enable(); > +#endif > } > > static inline __cpuidle void native_safe_halt(void) > { > mds_idle_clear_cpu_buffers(); > asm volatile("sti; hlt": : :"memory"); > +#ifdef CONFIG_AMD_MEM_ENCRYPT > + check_hv_pending_irq_enable(); > +#endif > } > > static inline __cpuidle void native_halt(void) > diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c > index a8862a2eff67..fe5e5e41433d 100644 > --- a/arch/x86/kernel/sev.c > +++ b/arch/x86/kernel/sev.c > @@ -179,6 +179,45 @@ void noinstr __sev_es_ist_enter(struct pt_regs *regs) > this_cpu_write(cpu_tss_rw.x86_tss.ist[IST_INDEX_VC], new_ist); > } > > +static void do_exc_hv(struct pt_regs *regs) > +{ > + /* Handle #HV exception. */ > +} > + > +void check_hv_pending(struct pt_regs *regs) > +{ > + if (!cc_platform_has(CC_ATTR_GUEST_SEV_SNP)) > + return; > + > + if ((regs->flags & X86_EFLAGS_IF) == 0) > + return;
Will this return and prevent guest from executing NMI's while irqs are disabled?
Thanks, Pankaj
> + > + do_exc_hv(regs); > +} > + > +void check_hv_pending_irq_enable(void) > +{ > + unsigned long flags; > + struct pt_regs regs; > + > + if (!cc_platform_has(CC_ATTR_GUEST_SEV_SNP)) > + return; > + > + memset(®s, 0, sizeof(struct pt_regs)); > + asm volatile("movl %%cs, %%eax;" : "=a" (regs.cs)); > + asm volatile("movl %%ss, %%eax;" : "=a" (regs.ss)); > + regs.orig_ax = 0xffffffff; > + regs.flags = native_save_fl(); > + > + /* > + * Disable irq when handle pending #HV events after > + * re-enabling irq. > + */ > + asm volatile("cli" : : : "memory"); > + do_exc_hv(®s); > + asm volatile("sti" : : : "memory"); > +} > + > void noinstr __sev_es_ist_exit(void) > { > unsigned long ist;
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