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Message-ID: <DM5PR03MB2490A3E5A6DEB22249884DECA0900@DM5PR03MB2490.namprd03.prod.outlook.com>
Date: Tue, 20 Dec 2016 20:57:28 +0000
From: KY Srinivasan <kys@...rosoft.com>
To: Roman Kagan <rkagan@...tuozzo.com>,
Paolo Bonzini <pbonzini@...hat.com>,
Radim Krčmář <rkrcmar@...hat.com>,
Vitaly Kuznetsov <vkuznets@...hat.com>
CC: Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>,
"H. Peter Anvin" <hpa@...or.com>,
"x86@...nel.org" <x86@...nel.org>,
"Haiyang Zhang" <haiyangz@...rosoft.com>,
"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"devel@...uxdriverproject.org" <devel@...uxdriverproject.org>,
"Denis V . Lunev" <den@...nvz.org>
Subject: RE: [PATCH 01/15] hyperv: consolidate TSC ref page definitions
> -----Original Message-----
> From: Roman Kagan [mailto:rkagan@...tuozzo.com]
> Sent: Tuesday, December 20, 2016 7:56 AM
> To: Paolo Bonzini <pbonzini@...hat.com>; Radim Krčmář
> <rkrcmar@...hat.com>; KY Srinivasan <kys@...rosoft.com>; Vitaly
> Kuznetsov <vkuznets@...hat.com>
> Cc: Thomas Gleixner <tglx@...utronix.de>; Ingo Molnar
> <mingo@...hat.com>; H. Peter Anvin <hpa@...or.com>; x86@...nel.org;
> Haiyang Zhang <haiyangz@...rosoft.com>; kvm@...r.kernel.org; linux-
> kernel@...r.kernel.org; devel@...uxdriverproject.org; Denis V . Lunev
> <den@...nvz.org>; Roman Kagan <rkagan@...tuozzo.com>
> Subject: [PATCH 01/15] hyperv: consolidate TSC ref page definitions
>
> Consolidate the guest-side and kvm-side definitions for Hyper-V TSC
> reference page.
>
> While at this, rewrite read_hv_clock_tsc using the existing helpers.
Why not beak this into separate patches.
>
> Signed-off-by: Roman Kagan <rkagan@...tuozzo.com>
> ---
> arch/x86/include/asm/kvm_host.h | 2 +-
> arch/x86/include/uapi/asm/hyperv.h | 4 +--
> drivers/hv/hyperv_vmbus.h | 8 ------
> arch/x86/kvm/hyperv.c | 4 +--
> drivers/hv/hv.c | 54 +++++++++++++++-----------------------
> 5 files changed, 26 insertions(+), 46 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm_host.h
> b/arch/x86/include/asm/kvm_host.h
> index 2e25038..2b85f49 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -713,7 +713,7 @@ struct kvm_hv {
> u64 hv_crash_param[HV_X64_MSR_CRASH_PARAMS];
> u64 hv_crash_ctl;
>
> - HV_REFERENCE_TSC_PAGE tsc_ref;
> + struct hv_ref_tsc_page tsc_ref;
> };
>
> struct kvm_arch {
> diff --git a/arch/x86/include/uapi/asm/hyperv.h
> b/arch/x86/include/uapi/asm/hyperv.h
> index 9b1a918..6098ab5 100644
> --- a/arch/x86/include/uapi/asm/hyperv.h
> +++ b/arch/x86/include/uapi/asm/hyperv.h
> @@ -252,12 +252,12 @@
> #define HV_STATUS_INVALID_CONNECTION_ID 18
> #define HV_STATUS_INSUFFICIENT_BUFFERS 19
>
> -typedef struct _HV_REFERENCE_TSC_PAGE {
> +struct hv_ref_tsc_page {
> __u32 tsc_sequence;
> __u32 res1;
> __u64 tsc_scale;
> __s64 tsc_offset;
> -} HV_REFERENCE_TSC_PAGE, *PHV_REFERENCE_TSC_PAGE;
> +};
>
> /* Define the number of synthetic interrupt sources. */
> #define HV_SYNIC_SINT_COUNT (16)
> diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h
> index 0675b39..4516498 100644
> --- a/drivers/hv/hyperv_vmbus.h
> +++ b/drivers/hv/hyperv_vmbus.h
> @@ -475,14 +475,6 @@ struct hv_context {
>
> extern struct hv_context hv_context;
>
> -struct ms_hyperv_tsc_page {
> - volatile u32 tsc_sequence;
> - u32 reserved1;
> - volatile u64 tsc_scale;
> - volatile s64 tsc_offset;
> - u64 reserved2[509];
> -};
> -
> struct hv_ring_buffer_debug_info {
> u32 current_interrupt_mask;
> u32 current_read_index;
> diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
> index 1572c35..c7db112 100644
> --- a/arch/x86/kvm/hyperv.c
> +++ b/arch/x86/kvm/hyperv.c
> @@ -806,7 +806,7 @@ static int kvm_hv_msr_set_crash_data(struct
> kvm_vcpu *vcpu,
> * These two equivalencies are implemented in this function.
> */
> static bool compute_tsc_page_parameters(struct pvclock_vcpu_time_info
> *hv_clock,
> - HV_REFERENCE_TSC_PAGE *tsc_ref)
> + struct hv_ref_tsc_page *tsc_ref)
> {
> u64 max_mul;
>
> @@ -847,7 +847,7 @@ void kvm_hv_setup_tsc_page(struct kvm *kvm,
> u64 gfn;
>
> BUILD_BUG_ON(sizeof(tsc_seq) != sizeof(hv-
> >tsc_ref.tsc_sequence));
> - BUILD_BUG_ON(offsetof(HV_REFERENCE_TSC_PAGE,
> tsc_sequence) != 0);
> + BUILD_BUG_ON(offsetof(struct hv_ref_tsc_page, tsc_sequence) !=
> 0);
>
> if (!(hv->hv_tsc_page & HV_X64_MSR_TSC_REFERENCE_ENABLE))
> return;
> diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
> index 446802a..a7256ec 100644
> --- a/drivers/hv/hv.c
> +++ b/drivers/hv/hv.c
> @@ -137,41 +137,29 @@ EXPORT_SYMBOL_GPL(hv_do_hypercall);
> #ifdef CONFIG_X86_64
> static cycle_t read_hv_clock_tsc(struct clocksource *arg)
> {
> - cycle_t current_tick;
> - struct ms_hyperv_tsc_page *tsc_pg = hv_context.tsc_page;
> + struct hv_ref_tsc_page *tsc_pg = hv_context.tsc_page;
> + u32 sequence;
> + u64 scale;
> + s64 offset;
> +
> + do {
> + sequence = tsc_pg->tsc_sequence;
> + virt_rmb();
> +
> + if (!sequence) {
> + /* fallback to MSR */
> + cycle_t current_tick;
> + rdmsrl(HV_X64_MSR_TIME_REF_COUNT,
> current_tick);
> + return current_tick;
> + }
>
> - if (tsc_pg->tsc_sequence != 0) {
> - /*
> - * Use the tsc page to compute the value.
> - */
> + scale = tsc_pg->tsc_scale;
> + offset = tsc_pg->tsc_offset;
>
> - while (1) {
> - cycle_t tmp;
> - u32 sequence = tsc_pg->tsc_sequence;
> - u64 cur_tsc;
> - u64 scale = tsc_pg->tsc_scale;
> - s64 offset = tsc_pg->tsc_offset;
> -
> - rdtscll(cur_tsc);
> - /* current_tick = ((cur_tsc *scale) >> 64) + offset */
> - asm("mulq %3"
> - : "=d" (current_tick), "=a" (tmp)
> - : "a" (cur_tsc), "r" (scale));
> -
> - current_tick += offset;
> - if (tsc_pg->tsc_sequence == sequence)
> - return current_tick;
> -
> - if (tsc_pg->tsc_sequence != 0)
> - continue;
> - /*
> - * Fallback using MSR method.
> - */
> - break;
> - }
> - }
> - rdmsrl(HV_X64_MSR_TIME_REF_COUNT, current_tick);
> - return current_tick;
> + virt_rmb();
> + } while (tsc_pg->tsc_sequence != sequence);
> +
> + return mul_u64_u64_shr(rdtsc_ordered(), scale, 64) + offset;
> }
>
> static struct clocksource hyperv_cs_tsc = {
> --
> 2.9.3
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