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authorChristoffer Dall <cdall@linaro.org>2017-08-31 23:24:25 +0300
committerChristoffer Dall <cdall@linaro.org>2017-09-05 18:33:39 +0300
commit9b87e7a8bfb5098129836757608b3cbbdc11245a (patch)
tree915298210e091afabb92388d32e7256e853d9d96 /Documentation/virtual
parent50f5bd5718df9e71d1f4ba69a6480dbad54b2f24 (diff)
downloadlinux-9b87e7a8bfb5098129836757608b3cbbdc11245a.tar.xz
KVM: arm/arm64: Support uaccess of GICC_APRn
When migrating guests around we need to know the active priorities to ensure functional virtual interrupt prioritization by the GIC. This commit clarifies the API and how active priorities of interrupts in different groups are represented, and implements the accessor functions for the uaccess register range. We live with a slight layering violation in accessing GICv3 data structures from vgic-mmio-v2.c, because anything else just adds too much complexity for us to deal with (it's not like there's a benefit elsewhere in the code of an intermediate representation as is the case with the VMCR). We accept this, because while doing v3 processing from a file named something-v2.c can look strange at first, this really is specific to dealing with the user space interface for something that looks like a GICv2. Reviewed-by: Marc Zyngier <marc.zyngier@arm.com> Signed-off-by: Christoffer Dall <cdall@linaro.org>
Diffstat (limited to 'Documentation/virtual')
-rw-r--r--Documentation/virtual/kvm/devices/arm-vgic.txt5
1 files changed, 5 insertions, 0 deletions
diff --git a/Documentation/virtual/kvm/devices/arm-vgic.txt b/Documentation/virtual/kvm/devices/arm-vgic.txt
index b2f60ca8b60c..b3ce12643553 100644
--- a/Documentation/virtual/kvm/devices/arm-vgic.txt
+++ b/Documentation/virtual/kvm/devices/arm-vgic.txt
@@ -83,6 +83,11 @@ Groups:
Bits for undefined preemption levels are RAZ/WI.
+ Note that this differs from a CPU's view of the APRs on hardware in which
+ a GIC without the security extensions expose group 0 and group 1 active
+ priorities in separate register groups, whereas we show a combined view
+ similar to GICv2's GICH_APR.
+
For historical reasons and to provide ABI compatibility with userspace we
export the GICC_PMR register in the format of the GICH_VMCR.VMPriMask
field in the lower 5 bits of a word, meaning that userspace must always