Re: [RFC PATCH 01/28] OvmfPkg/Sec: Enable cache early to speed up booting

Jordan Justen

On 2019-08-21 07:21:25, Laszlo Ersek wrote:
On 08/19/19 23:35, Lendacky, Thomas wrote:
From: Tom Lendacky <>

Currently, the OVMF code relies on the hypervisor to enable the cache
support on the processor in order to improve the boot speed. However,
with SEV-ES, the hypervisor is not allowed to change the CR0 register
to enable caching.

Update the OVMF Sec support to enable caching in order to improve the
boot speed.

Signed-off-by: Tom Lendacky <>
OvmfPkg/Sec/SecMain.c | 5 +++++
1 file changed, 5 insertions(+)

diff --git a/OvmfPkg/Sec/SecMain.c b/OvmfPkg/Sec/SecMain.c
index 3914355cd17b..2448be0cd408 100644
--- a/OvmfPkg/Sec/SecMain.c
+++ b/OvmfPkg/Sec/SecMain.c
@@ -739,6 +739,11 @@ SecCoreStartupWithStack (

ProcessLibraryConstructorList (NULL, NULL);

+ //
+ // Enable caching
+ //
+ AsmEnableCache ();
"SecCoreStartupWithStack(0x%x, 0x%x)\n",
This makes me uncomfortable. There used to be problems related to
caching when VFIO device assignment were used. My concern is admittedly
vague, but this is a very brittle area of OVMF-on-KVM. If you asked me
"well what could break here", I'd answer "you never know, and the burden
of proof is not on me". :) Can we make this change conditional on SEV-ES?
This was also raised as an issue by Peter for the ACRN hypervisor and
Scott for the bhyve hypervisor.

I think it is rare for a platform to enable cache at this early of a
stage, but it is also rare to decompress a firmware volume at this

It appears that it could be helpful to figure out how to safely enable
cache by default here, since it does seem to be impacting several


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