[edk2-devel] [PATCH v2 01/11] OvmfPkg: introduce PcdQ35SmramAtDefaultSmbase

[Laszlo Ersek]

For supporting VCPU hotplug with SMM enabled/required, QEMU offers the
(dynamically detectable) feature called "SMRAM at default SMBASE". When
the feature is enabled, the firmware can lock down the 128 KB range
starting at the default SMBASE; that is, the [0x3_0000, 0x4_FFFF]
interval. The goal is to shield the very first SMI handler of the
hotplugged VCPU from OS influence.

Multiple modules in OVMF will have to inter-operate for locking down this
range. Introduce a dynamic PCD that will reflect the feature (to be
negotiated by PlatformPei), for coordination between drivers.

Cc: Ard Biesheuvel <ard.biesheuvel at linaro.org>
Cc: Jordan Justen <jordan.l.justen at intel.com>
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=1512
Signed-off-by: Laszlo Ersek <lersek at redhat.com>
Reviewed-by: Jiewen Yao <jiewen.yao at intel.com>
---

Notes:
    v2:
    - trim Cc list
    - pick up Jiewen's R-b <https://edk2.groups.io/g/devel/message/48166>

 OvmfPkg/OvmfPkg.dec        | 6 ++++++
 OvmfPkg/OvmfPkgIa32.dsc    | 1 +
 OvmfPkg/OvmfPkgIa32X64.dsc | 1 +
 OvmfPkg/OvmfPkgX64.dsc     | 1 +
 4 files changed, 9 insertions(+)

diff --git a/OvmfPkg/OvmfPkg.dec b/OvmfPkg/OvmfPkg.dec
index d5fee805ef4a..57034c784f88 100644
--- a/OvmfPkg/OvmfPkg.dec
+++ b/OvmfPkg/OvmfPkg.dec
@@ -257,6 +257,12 @@ [PcdsDynamic, PcdsDynamicEx]
   #  This PCD is only accessed if PcdSmmSmramRequire is TRUE (see below).
   gUefiOvmfPkgTokenSpaceGuid.PcdQ35TsegMbytes|8|UINT16|0x20
 
+  ## Set to TRUE by PlatformPei if the Q35 board supports the "SMRAM at default
+  #  SMBASE" feature.
+  #
+  #  This PCD is only accessed if PcdSmmSmramRequire is TRUE (see below).
+  gUefiOvmfPkgTokenSpaceGuid.PcdQ35SmramAtDefaultSmbase|FALSE|BOOLEAN|0x34
+
 [PcdsFeatureFlag]
   gUefiOvmfPkgTokenSpaceGuid.PcdQemuBootOrderPciTranslation|TRUE|BOOLEAN|0x1c
   gUefiOvmfPkgTokenSpaceGuid.PcdQemuBootOrderMmioTranslation|FALSE|BOOLEAN|0x1d
diff --git a/OvmfPkg/OvmfPkgIa32.dsc b/OvmfPkg/OvmfPkgIa32.dsc
index 4568b78cadf1..43ff51933609 100644
--- a/OvmfPkg/OvmfPkgIa32.dsc
+++ b/OvmfPkg/OvmfPkgIa32.dsc
@@ -565,6 +565,7 @@ [PcdsDynamicDefault]
 
 !if $(SMM_REQUIRE) == TRUE
   gUefiOvmfPkgTokenSpaceGuid.PcdQ35TsegMbytes|8
+  gUefiOvmfPkgTokenSpaceGuid.PcdQ35SmramAtDefaultSmbase|FALSE
   gUefiCpuPkgTokenSpaceGuid.PcdCpuSmmSyncMode|0x01
   gUefiCpuPkgTokenSpaceGuid.PcdCpuSmmApSyncTimeout|100000
 !endif
diff --git a/OvmfPkg/OvmfPkgIa32X64.dsc b/OvmfPkg/OvmfPkgIa32X64.dsc
index 152b5d067116..5b3e217e9220 100644
--- a/OvmfPkg/OvmfPkgIa32X64.dsc
+++ b/OvmfPkg/OvmfPkgIa32X64.dsc
@@ -577,6 +577,7 @@ [PcdsDynamicDefault]
 
 !if $(SMM_REQUIRE) == TRUE
   gUefiOvmfPkgTokenSpaceGuid.PcdQ35TsegMbytes|8
+  gUefiOvmfPkgTokenSpaceGuid.PcdQ35SmramAtDefaultSmbase|FALSE
   gUefiCpuPkgTokenSpaceGuid.PcdCpuSmmSyncMode|0x01
   gUefiCpuPkgTokenSpaceGuid.PcdCpuSmmApSyncTimeout|100000
 !endif
diff --git a/OvmfPkg/OvmfPkgX64.dsc b/OvmfPkg/OvmfPkgX64.dsc
index 4bfad441bd9f..a378d0a449aa 100644
--- a/OvmfPkg/OvmfPkgX64.dsc
+++ b/OvmfPkg/OvmfPkgX64.dsc
@@ -576,6 +576,7 @@ [PcdsDynamicDefault]
 
 !if $(SMM_REQUIRE) == TRUE
   gUefiOvmfPkgTokenSpaceGuid.PcdQ35TsegMbytes|8
+  gUefiOvmfPkgTokenSpaceGuid.PcdQ35SmramAtDefaultSmbase|FALSE
   gUefiCpuPkgTokenSpaceGuid.PcdCpuSmmSyncMode|0x01
   gUefiCpuPkgTokenSpaceGuid.PcdCpuSmmApSyncTimeout|100000
 !endif
-- 
2.19.1.3.g30247aa5d201



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