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Message-ID: <5669415E.9080408@redhat.com>
Date: Thu, 10 Dec 2015 10:09:50 +0100
From: Paolo Bonzini <pbonzini@...hat.com>
To: Andy Lutomirski <luto@...nel.org>, x86@...nel.org,
Marcelo Tosatti <mtosatti@...hat.com>,
Radim Krcmar <rkrcmar@...hat.com>
Cc: linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
Alexander Graf <agraf@...e.de>
Subject: Re: [PATCH 3/5] x86/vdso: Get pvclock data from the vvar VMA instead
of the fixmap
On 10/12/2015 00:12, Andy Lutomirski wrote:
> Signed-off-by: Andy Lutomirski <luto@...nel.org>
> ---
> arch/x86/entry/vdso/vclock_gettime.c | 20 ++++++++------------
> arch/x86/entry/vdso/vdso-layout.lds.S | 3 ++-
> arch/x86/entry/vdso/vdso2c.c | 3 +++
> arch/x86/entry/vdso/vma.c | 13 +++++++++++++
> arch/x86/include/asm/pvclock.h | 9 +++++++++
> arch/x86/include/asm/vdso.h | 1 +
> arch/x86/kernel/kvmclock.c | 5 +++++
> 7 files changed, 41 insertions(+), 13 deletions(-)
>
> diff --git a/arch/x86/entry/vdso/vclock_gettime.c b/arch/x86/entry/vdso/vclock_gettime.c
> index c325ba1bdddf..5dd363d54348 100644
> --- a/arch/x86/entry/vdso/vclock_gettime.c
> +++ b/arch/x86/entry/vdso/vclock_gettime.c
> @@ -36,6 +36,11 @@ static notrace cycle_t vread_hpet(void)
> }
> #endif
>
> +#ifdef CONFIG_PARAVIRT_CLOCK
> +extern u8 pvclock_page
> + __attribute__((visibility("hidden")));
> +#endif
> +
> #ifndef BUILD_VDSO32
>
> #include <linux/kernel.h>
> @@ -62,23 +67,14 @@ notrace static long vdso_fallback_gtod(struct timeval *tv, struct timezone *tz)
>
> #ifdef CONFIG_PARAVIRT_CLOCK
>
> -static notrace const struct pvclock_vsyscall_time_info *get_pvti(int cpu)
> +static notrace const struct pvclock_vsyscall_time_info *get_pvti0(void)
> {
> - const struct pvclock_vsyscall_time_info *pvti_base;
> - int idx = cpu / (PAGE_SIZE/PVTI_SIZE);
> - int offset = cpu % (PAGE_SIZE/PVTI_SIZE);
> -
> - BUG_ON(PVCLOCK_FIXMAP_BEGIN + idx > PVCLOCK_FIXMAP_END);
> -
> - pvti_base = (struct pvclock_vsyscall_time_info *)
> - __fix_to_virt(PVCLOCK_FIXMAP_BEGIN+idx);
> -
> - return &pvti_base[offset];
> + return (const struct pvclock_vsyscall_time_info *)&pvclock_page;
> }
>
> static notrace cycle_t vread_pvclock(int *mode)
> {
> - const struct pvclock_vcpu_time_info *pvti = &get_pvti(0)->pvti;
> + const struct pvclock_vcpu_time_info *pvti = &get_pvti0()->pvti;
> cycle_t ret;
> u64 tsc, pvti_tsc;
> u64 last, delta, pvti_system_time;
> diff --git a/arch/x86/entry/vdso/vdso-layout.lds.S b/arch/x86/entry/vdso/vdso-layout.lds.S
> index de2c921025f5..4158acc17df0 100644
> --- a/arch/x86/entry/vdso/vdso-layout.lds.S
> +++ b/arch/x86/entry/vdso/vdso-layout.lds.S
> @@ -25,7 +25,7 @@ SECTIONS
> * segment.
> */
>
> - vvar_start = . - 2 * PAGE_SIZE;
> + vvar_start = . - 3 * PAGE_SIZE;
> vvar_page = vvar_start;
>
> /* Place all vvars at the offsets in asm/vvar.h. */
> @@ -36,6 +36,7 @@ SECTIONS
> #undef EMIT_VVAR
>
> hpet_page = vvar_start + PAGE_SIZE;
> + pvclock_page = vvar_start + 2 * PAGE_SIZE;
>
> . = SIZEOF_HEADERS;
>
> diff --git a/arch/x86/entry/vdso/vdso2c.c b/arch/x86/entry/vdso/vdso2c.c
> index 785d9922b106..491020b2826d 100644
> --- a/arch/x86/entry/vdso/vdso2c.c
> +++ b/arch/x86/entry/vdso/vdso2c.c
> @@ -73,6 +73,7 @@ enum {
> sym_vvar_start,
> sym_vvar_page,
> sym_hpet_page,
> + sym_pvclock_page,
> sym_VDSO_FAKE_SECTION_TABLE_START,
> sym_VDSO_FAKE_SECTION_TABLE_END,
> };
> @@ -80,6 +81,7 @@ enum {
> const int special_pages[] = {
> sym_vvar_page,
> sym_hpet_page,
> + sym_pvclock_page,
> };
>
> struct vdso_sym {
> @@ -91,6 +93,7 @@ struct vdso_sym required_syms[] = {
> [sym_vvar_start] = {"vvar_start", true},
> [sym_vvar_page] = {"vvar_page", true},
> [sym_hpet_page] = {"hpet_page", true},
> + [sym_pvclock_page] = {"pvclock_page", true},
> [sym_VDSO_FAKE_SECTION_TABLE_START] = {
> "VDSO_FAKE_SECTION_TABLE_START", false
> },
> diff --git a/arch/x86/entry/vdso/vma.c b/arch/x86/entry/vdso/vma.c
> index 64df47148160..aa828191c654 100644
> --- a/arch/x86/entry/vdso/vma.c
> +++ b/arch/x86/entry/vdso/vma.c
> @@ -100,6 +100,7 @@ static int map_vdso(const struct vdso_image *image, bool calculate_addr)
> .name = "[vvar]",
> .pages = no_pages,
> };
> + struct pvclock_vsyscall_time_info *pvti;
>
> if (calculate_addr) {
> addr = vdso_addr(current->mm->start_stack,
> @@ -169,6 +170,18 @@ static int map_vdso(const struct vdso_image *image, bool calculate_addr)
> }
> #endif
>
> + pvti = pvclock_pvti_cpu0_va();
> + if (pvti && image->sym_pvclock_page) {
> + ret = remap_pfn_range(vma,
> + text_start + image->sym_pvclock_page,
> + __pa(pvti) >> PAGE_SHIFT,
> + PAGE_SIZE,
> + PAGE_READONLY);
> +
> + if (ret)
> + goto up_fail;
> + }
> +
> up_fail:
> if (ret)
> current->mm->context.vdso = NULL;
> diff --git a/arch/x86/include/asm/pvclock.h b/arch/x86/include/asm/pvclock.h
> index 7a6bed5c08bc..3864398c7cb2 100644
> --- a/arch/x86/include/asm/pvclock.h
> +++ b/arch/x86/include/asm/pvclock.h
> @@ -4,6 +4,15 @@
> #include <linux/clocksource.h>
> #include <asm/pvclock-abi.h>
>
> +#ifdef CONFIG_PARAVIRT_CLOCK
> +extern struct pvclock_vsyscall_time_info *pvclock_pvti_cpu0_va(void);
> +#else
> +static inline struct pvclock_vsyscall_time_info *pvclock_pvti_cpu0_va(void)
> +{
> + return NULL;
> +}
> +#endif
> +
> /* some helper functions for xen and kvm pv clock sources */
> cycle_t pvclock_clocksource_read(struct pvclock_vcpu_time_info *src);
> u8 pvclock_read_flags(struct pvclock_vcpu_time_info *src);
> diff --git a/arch/x86/include/asm/vdso.h b/arch/x86/include/asm/vdso.h
> index 756de9190aec..deabaf9759b6 100644
> --- a/arch/x86/include/asm/vdso.h
> +++ b/arch/x86/include/asm/vdso.h
> @@ -22,6 +22,7 @@ struct vdso_image {
>
> long sym_vvar_page;
> long sym_hpet_page;
> + long sym_pvclock_page;
> long sym_VDSO32_NOTE_MASK;
> long sym___kernel_sigreturn;
> long sym___kernel_rt_sigreturn;
> diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c
> index 2bd81e302427..ec1b06dc82d2 100644
> --- a/arch/x86/kernel/kvmclock.c
> +++ b/arch/x86/kernel/kvmclock.c
> @@ -45,6 +45,11 @@ early_param("no-kvmclock", parse_no_kvmclock);
> static struct pvclock_vsyscall_time_info *hv_clock;
> static struct pvclock_wall_clock wall_clock;
>
> +struct pvclock_vsyscall_time_info *pvclock_pvti_cpu0_va(void)
> +{
> + return hv_clock;
> +}
> +
> /*
> * The wallclock is the time of day when we booted. Since then, some time may
> * have elapsed since the hypervisor wrote the data. So we try to account for
>
Acked-by: Paolo Bonzini <pbonzini@...hat.com>
--
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