From 9b147f96ae69cadafc853a544a7526b1740b053c Mon Sep 17 00:00:00 2001 From: Julien Grall Date: Tue, 22 Sep 2015 21:18:48 +0100 Subject: [PATCH] xen/arm: vgic: Correctly emulate write when byte is used When a guest is writing a byte, the value will be located in bits[7:0] of the register. Although the current implementation is expecting the byte at the Nth byte of the register where N = address & 4; When the address is not 4-byte aligned, the corresponding byte in the internal state will always be set to zero rather. Note that byte access are only used for GICD_IPRIORITYR and GICD_ITARGETSR. So the worst things that could happen is not setting the priority correctly and ignore the target vCPU written. Signed-off-by: Julien Grall Acked-by: Ian Campbell (cherry picked from commit 3f214fea76acc6cbc1101fe1815cee795483a67d) --- xen/include/asm-arm/vgic.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/xen/include/asm-arm/vgic.h b/xen/include/asm-arm/vgic.h index 74d5a4e3e3..cbe035e814 100644 --- a/xen/include/asm-arm/vgic.h +++ b/xen/include/asm-arm/vgic.h @@ -161,10 +161,10 @@ static inline void vgic_byte_write(uint32_t *reg, uint32_t var, int offset) { int byte = offset & 0x3; - var &= (0xff << (8*byte)); + var &= 0xff; *reg &= ~(0xff << (8*byte)); - *reg |= var; + *reg |= (var << (8*byte)); } enum gic_sgi_mode; -- 2.39.5