Calculate the frequency of the APIC timer that Xen provides. Even though the frequency is currently hard-coded, it isn't part of the public ABI that Xen provides and thus may change at any time. OVMF needs to determine the frequency by an other mean.
Fortunately, Xen provides a way to determines the frequency of the TSC, so we can use TSC to calibrate the frequency of the APIC timer. That information is found in the shared_info page which we map and unmap once done (XenBusDxe is going to map the page somewhere else). The shared_info page is map at the highest physical address allowed as it doesn't need to be in the RAM, thus there's a call to update the page table. The calculated frequency is only logged in this patch, it will be used in a following patch. Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=2490 Signed-off-by: Anthony PERARD <anthony.per...@citrix.com> --- CC: Roger Pau Monné <roger....@citrix.com> --- Notes: v2: - fix CamelCases - Use U64 multiplication and division helpers - don't read TscShift from the SharedInfo page again - change the location of the shared info page to be outside of the ram - check for overflow in XenDelay - check for overflow when calculating the calculating APIC frequency OvmfPkg/XenPlatformPei/XenPlatformPei.inf | 2 + OvmfPkg/XenPlatformPei/Platform.h | 5 + OvmfPkg/XenPlatformPei/Platform.c | 1 + OvmfPkg/XenPlatformPei/Xen.c | 177 ++++++++++++++++++++++ 4 files changed, 185 insertions(+) diff --git a/OvmfPkg/XenPlatformPei/XenPlatformPei.inf b/OvmfPkg/XenPlatformPei/XenPlatformPei.inf index 8790d907d3ec..5732d2188871 100644 --- a/OvmfPkg/XenPlatformPei/XenPlatformPei.inf +++ b/OvmfPkg/XenPlatformPei/XenPlatformPei.inf @@ -52,6 +52,7 @@ [LibraryClasses] DebugLib HobLib IoLib + LocalApicLib PciLib ResourcePublicationLib PeiServicesLib @@ -59,6 +60,7 @@ [LibraryClasses] MtrrLib MemEncryptSevLib PcdLib + SafeIntLib XenHypercallLib [Pcd] diff --git a/OvmfPkg/XenPlatformPei/Platform.h b/OvmfPkg/XenPlatformPei/Platform.h index e70ca58078eb..77d88fc159d7 100644 --- a/OvmfPkg/XenPlatformPei/Platform.h +++ b/OvmfPkg/XenPlatformPei/Platform.h @@ -132,6 +132,11 @@ PhysicalAddressIdentityMapping ( IN EFI_PHYSICAL_ADDRESS AddressToMap ); +VOID +CalibrateLapicTimer ( + VOID + ); + extern EFI_BOOT_MODE mBootMode; extern UINT8 mPhysMemAddressWidth; diff --git a/OvmfPkg/XenPlatformPei/Platform.c b/OvmfPkg/XenPlatformPei/Platform.c index 717fd0ab1a45..e9511eb40c62 100644 --- a/OvmfPkg/XenPlatformPei/Platform.c +++ b/OvmfPkg/XenPlatformPei/Platform.c @@ -448,6 +448,7 @@ InitializeXenPlatform ( InitializeRamRegions (); InitializeXen (); + CalibrateLapicTimer (); if (mBootMode != BOOT_ON_S3_RESUME) { ReserveEmuVariableNvStore (); diff --git a/OvmfPkg/XenPlatformPei/Xen.c b/OvmfPkg/XenPlatformPei/Xen.c index b2a7d1c21dac..7524aaa11a29 100644 --- a/OvmfPkg/XenPlatformPei/Xen.c +++ b/OvmfPkg/XenPlatformPei/Xen.c @@ -21,8 +21,10 @@ #include <Library/CpuLib.h> #include <Library/DebugLib.h> #include <Library/HobLib.h> +#include <Library/LocalApicLib.h> #include <Library/MemoryAllocationLib.h> #include <Library/PcdLib.h> +#include <Library/SafeIntLib.h> #include <Guid/XenInfo.h> #include <IndustryStandard/E820.h> #include <Library/ResourcePublicationLib.h> @@ -457,3 +459,178 @@ PhysicalAddressIdentityMapping ( return EFI_SUCCESS; } + +STATIC +EFI_STATUS +MapSharedInfoPage ( + IN VOID *PagePtr + ) +{ + xen_add_to_physmap_t Parameters; + INTN ReturnCode; + + Parameters.domid = DOMID_SELF; + Parameters.space = XENMAPSPACE_shared_info; + Parameters.idx = 0; + Parameters.gpfn = (UINTN)PagePtr >> EFI_PAGE_SHIFT; + ReturnCode = XenHypercallMemoryOp (XENMEM_add_to_physmap, &Parameters); + if (ReturnCode != 0) { + return EFI_NO_MAPPING; + } + return EFI_SUCCESS; +} + +STATIC +VOID +UnmapXenPage ( + IN VOID *PagePtr + ) +{ + xen_remove_from_physmap_t Parameters; + INTN ReturnCode; + + Parameters.domid = DOMID_SELF; + Parameters.gpfn = (UINTN)PagePtr >> EFI_PAGE_SHIFT; + ReturnCode = XenHypercallMemoryOp (XENMEM_remove_from_physmap, &Parameters); + ASSERT (ReturnCode == 0); +} + + +STATIC +UINT64 +GetCpuFreq ( + IN XEN_VCPU_TIME_INFO *VcpuTime + ) +{ + UINT32 Version; + UINT32 TscToSystemMultiplier; + INT8 TscShift; + UINT64 CpuFreq; + + do { + Version = VcpuTime->Version; + MemoryFence (); + TscToSystemMultiplier = VcpuTime->TscToSystemMultiplier; + TscShift = VcpuTime->TscShift; + MemoryFence (); + } while (((Version & 1) != 0) && (Version != VcpuTime->Version)); + + CpuFreq = DivU64x32 (LShiftU64 (1000000000ULL, 32), TscToSystemMultiplier); + if (TscShift >= 0) { + CpuFreq = RShiftU64 (CpuFreq, TscShift); + } else { + CpuFreq = LShiftU64 (CpuFreq, -TscShift); + } + return CpuFreq; +} + +STATIC +VOID +XenDelay ( + IN XEN_VCPU_TIME_INFO *VcpuTimeInfo, + IN UINT64 DelayNs + ) +{ + UINT64 Tick; + UINT64 CpuFreq; + UINT64 Delay; + UINT64 DelayTick; + UINT64 NewTick; + RETURN_STATUS Status; + + Tick = AsmReadTsc (); + + CpuFreq = GetCpuFreq (VcpuTimeInfo); + Status = SafeUint64Mult (DelayNs, CpuFreq, &Delay); + ASSERT_EFI_ERROR (Status); + if (EFI_ERROR (Status)) { + DEBUG ((DEBUG_ERROR, + "XenDelay (%ld ns): delay too big in relation to CPU freq %ld Hz\n", + DelayNs, CpuFreq)); + CpuDeadLoop (); + } + + DelayTick = DivU64x32 (Delay, 1000000000UL); + + NewTick = Tick + DelayTick; + + // + // Check for overflow + // + if (NewTick < Tick) { + // + // Overflow, wait for TSC to also overflow + // + while (AsmReadTsc () >= Tick) { + CpuPause (); + } + } + + while (AsmReadTsc () <= NewTick) { + CpuPause (); + } +} + + +/** + Calculate the frequency of the Local Apic Timer +**/ +VOID +CalibrateLapicTimer ( + VOID + ) +{ + XEN_SHARED_INFO *SharedInfo; + XEN_VCPU_TIME_INFO *VcpuTimeInfo; + UINT32 TimerTick, TimerTick2, DiffTimer; + UINT64 TscTick, TscTick2; + UINT64 Freq; + UINT64 Dividend; + EFI_STATUS Status; + + + SharedInfo = (VOID*)((1ULL << mPhysMemAddressWidth) - EFI_PAGE_SIZE); + Status = PhysicalAddressIdentityMapping ((EFI_PHYSICAL_ADDRESS)SharedInfo); + ASSERT_EFI_ERROR (Status); + if (EFI_ERROR (Status)) { + DEBUG ((DEBUG_ERROR, + "Failed to add page table entry for Xen shared info page: %r\n", + Status)); + return; + } + + Status = MapSharedInfoPage (SharedInfo); + ASSERT_EFI_ERROR (Status); + if (EFI_ERROR (Status)) { + DEBUG ((DEBUG_ERROR, "Failed to map Xen's shared info page: %r\n", + Status)); + return; + } + + VcpuTimeInfo = &SharedInfo->VcpuInfo[0].Time; + + InitializeApicTimer (1, MAX_UINT32, TRUE, 0); + DisableApicTimerInterrupt (); + + TimerTick = GetApicTimerCurrentCount (); + TscTick = AsmReadTsc (); + XenDelay (VcpuTimeInfo, 1000000ULL); + TimerTick2 = GetApicTimerCurrentCount (); + TscTick2 = AsmReadTsc (); + + + DiffTimer = TimerTick - TimerTick2; + Status = SafeUint64Mult (GetCpuFreq (VcpuTimeInfo), DiffTimer, &Dividend); + ASSERT_EFI_ERROR (Status); + if (EFI_ERROR (Status)) { + DEBUG ((DEBUG_ERROR, "overflow while calculating APIC frequency\n")); + DEBUG ((DEBUG_ERROR, "CPU freq: %ld Hz; APIC timer tick count for 1 ms: %d\n", + GetCpuFreq (VcpuTimeInfo), DiffTimer)); + CpuDeadLoop (); + } + + Freq = DivU64x64Remainder (Dividend, TscTick2 - TscTick, NULL); + DEBUG ((DEBUG_INFO, "APIC Freq % 8lu Hz\n", Freq)); + + UnmapXenPage (SharedInfo); +} -- Anthony PERARD -=-=-=-=-=-=-=-=-=-=-=- Groups.io Links: You receive all messages sent to this group. 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