Re: [Xen-devel] [PATCH 5/5] OvmfPkg/OvmfXen: Set PcdFSBClock

[Laszlo Ersek <lersek@xxxxxxxxxx>]

On 01/29/20 13:12, Anthony PERARD wrote:
> Update gEfiMdePkgTokenSpaceGuid.PcdFSBClock so it can have the correct
> value when SecPeiDxeTimerLibCpu start to use it for the APIC timer.
> 
> Currently, nothing appear to use the value in PcdFSBClock before
> XenPlatformPei had a chance to set it even though TimerLib is included
> in modules runned before XenPlatformPei.
> 
> XenPlatformPei doesn't use any of the functions that would use that
> value. No other modules in the PEI phase seems to use the TimerLib
> before PcdFSBClock is set. There are currently two other modules in
> the PEI phase that needs the TimerLib:
> - S3Resume2Pei, but only because LocalApicLib needs it, but nothing is
>   using the value from PcdFSBClock.
> - CpuMpPei, but I believe it only runs after XenPlatformPei
> 
> Before the PEI phase, there's the SEC phase, and SecMain needs
> TimerLib because of LocalApicLib. And it initialise the APIC timers
> for the debug agent. But I don't think any of the DebugLib that
> OvmfXen could use are actually using the *Delay functions in TimerLib,
> and so would not use the value from PcdFSBClock which would be
> uninitialised.
> 
> A simple runtime test showed that TimerLib doesn't use PcdFSBClock
> value before it is set.
> 
> Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=2490
> Signed-off-by: Anthony PERARD <anthony.perard@xxxxxxxxxx>
> ---
>  OvmfPkg/OvmfXen.dsc                       | 4 +---
>  OvmfPkg/XenPlatformPei/XenPlatformPei.inf | 1 +
>  OvmfPkg/XenPlatformPei/Xen.c              | 4 ++++
>  3 files changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/OvmfPkg/OvmfXen.dsc b/OvmfPkg/OvmfXen.dsc
> index 8c11efe9b709..190d7400c148 100644
> --- a/OvmfPkg/OvmfXen.dsc
> +++ b/OvmfPkg/OvmfXen.dsc
> @@ -442,9 +442,6 @@ [PcdsFixedAtBuild]
>    # Point to the MdeModulePkg/Application/UiApp/UiApp.inf
>    gEfiMdeModulePkgTokenSpaceGuid.PcdBootManagerMenuFile|{ 0x21, 0xaa, 0x2c, 
> 0x46, 0x14, 0x76, 0x03, 0x45, 0x83, 0x6e, 0x8a, 0xb6, 0xf4, 0x66, 0x23, 0x31 }
>  
> -  ## Xen vlapic's frequence is 100 MHz
> -  gEfiMdePkgTokenSpaceGuid.PcdFSBClock|100000000
> -
>  
> ################################################################################
>  #
>  # Pcd Dynamic Section - list of all EDK II PCD Entries defined by this 
> Platform
> @@ -468,6 +465,7 @@ [PcdsDynamicDefault]
>    gUefiOvmfPkgTokenSpaceGuid.PcdPciMmio64Base|0x0
>    gUefiOvmfPkgTokenSpaceGuid.PcdPciMmio64Size|0x800000000
>  
> +  gEfiMdePkgTokenSpaceGuid.PcdFSBClock

(1) This syntax looks strange; I thought it was mandatory to provide a
default value too.

https://edk2-docs.gitbooks.io/edk-ii-dsc-specification/content/2_dsc_overview/28_pcd_sections.html

---------
2.8.3.1 PcdsDynamicDefault

[...]

The format for a boolean or numeric datum type PCD entry in this section is:

PcdTokenSpaceGuidCName.PcdCName|Value
---------

I'm not sure if the "build" utility accepts this intentionally, or by
mistake.

Can you simply keep the "|100000000" part too?

Otherwise, I'm OK with the argument laid out in the commit message.
(Thank you for the detailed commit message!)

With (1) fixed:

Reviewed-by: Laszlo Ersek <lersek@xxxxxxxxxx>

Thanks!
Laszlo


>    gEfiMdePkgTokenSpaceGuid.PcdPlatformBootTimeOut|0
>  
>    # Set video resolution for text setup.
> diff --git a/OvmfPkg/XenPlatformPei/XenPlatformPei.inf 
> b/OvmfPkg/XenPlatformPei/XenPlatformPei.inf
> index 335a442538c2..177200f3b7e5 100644
> --- a/OvmfPkg/XenPlatformPei/XenPlatformPei.inf
> +++ b/OvmfPkg/XenPlatformPei/XenPlatformPei.inf
> @@ -83,6 +83,7 @@ [Pcd]
>    gEfiMdeModulePkgTokenSpaceGuid.PcdDxeIplSwitchToLongMode
>    gEfiMdeModulePkgTokenSpaceGuid.PcdUse1GPageTable
>    gEfiMdeModulePkgTokenSpaceGuid.PcdPteMemoryEncryptionAddressOrMask
> +  gEfiMdePkgTokenSpaceGuid.PcdFSBClock
>    gEfiSecurityPkgTokenSpaceGuid.PcdOptionRomImageVerificationPolicy
>    gUefiCpuPkgTokenSpaceGuid.PcdCpuLocalApicBaseAddress
>  
> diff --git a/OvmfPkg/XenPlatformPei/Xen.c b/OvmfPkg/XenPlatformPei/Xen.c
> index d6cdc9a8e31c..fc990462dccc 100644
> --- a/OvmfPkg/XenPlatformPei/Xen.c
> +++ b/OvmfPkg/XenPlatformPei/Xen.c
> @@ -504,6 +504,10 @@ CalibrateLapicTimer (
>      / (TscTick2 - TscTick);
>    DEBUG ((DEBUG_INFO, "APIC Freq % 8lu Hz\n", Freq));
>  
> +  ASSERT (Freq <= MAX_UINT32);
> +  Status = PcdSet32S (PcdFSBClock, Freq);
> +  ASSERT_RETURN_ERROR (Status);
> +
>    UnmapXenPage (SharedInfo);
>  
>  Exit:
> 


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