From: Sairaj Kodilkar <sarun...@amd.com>
amdvi_write*() function do not preserve the older values of W1C bits in
the MMIO register. This results in all W1C bits set to 0, when guest
tries to reset a single bit by writing 1 to it. Fix this by preserving
W1C bits in the old value of the MMIO register.
Fixes: d29a09ca68428 ("hw/i386: Introduce AMD IOMMU")
Suggested-by: Ethan MILON <ethan.mi...@eviden.com>
Signed-off-by: Sairaj Kodilkar <sarun...@amd.com>
Message-Id: <20250801060507.3382-5-sarun...@amd.com>
Reviewed-by: Michael S. Tsirkin <m...@redhat.com>
Signed-off-by: Michael S. Tsirkin <m...@redhat.com>
---
hw/i386/amd_iommu.c | 21 ++++++++++++++++++---
1 file changed, 18 insertions(+), 3 deletions(-)
diff --git a/hw/i386/amd_iommu.c b/hw/i386/amd_iommu.c
index 7308611bf1..c9c32cf7b0 100644
--- a/hw/i386/amd_iommu.c
+++ b/hw/i386/amd_iommu.c
@@ -123,8 +123,13 @@ static void amdvi_writew(AMDVIState *s, hwaddr addr,
uint16_t val)
uint16_t romask = lduw_le_p(&s->romask[addr]);
uint16_t w1cmask = lduw_le_p(&s->w1cmask[addr]);
uint16_t oldval = lduw_le_p(&s->mmior[addr]);
+
+ uint16_t oldval_preserved = oldval & (romask | w1cmask);
+ uint16_t newval_write = val & ~romask;
+ uint16_t newval_w1c_set = val & w1cmask;
+
stw_le_p(&s->mmior[addr],
- ((oldval & romask) | (val & ~romask)) & ~(val & w1cmask));
+ (oldval_preserved | newval_write) & ~newval_w1c_set);
}
static void amdvi_writel(AMDVIState *s, hwaddr addr, uint32_t val)
@@ -132,8 +137,13 @@ static void amdvi_writel(AMDVIState *s, hwaddr addr,
uint32_t val)
uint32_t romask = ldl_le_p(&s->romask[addr]);
uint32_t w1cmask = ldl_le_p(&s->w1cmask[addr]);
uint32_t oldval = ldl_le_p(&s->mmior[addr]);
+
+ uint32_t oldval_preserved = oldval & (romask | w1cmask);
+ uint32_t newval_write = val & ~romask;
+ uint32_t newval_w1c_set = val & w1cmask;
+
stl_le_p(&s->mmior[addr],
- ((oldval & romask) | (val & ~romask)) & ~(val & w1cmask));
+ (oldval_preserved | newval_write) & ~newval_w1c_set);
}
static void amdvi_writeq(AMDVIState *s, hwaddr addr, uint64_t val)
@@ -141,8 +151,13 @@ static void amdvi_writeq(AMDVIState *s, hwaddr addr,
uint64_t val)
uint64_t romask = ldq_le_p(&s->romask[addr]);
uint64_t w1cmask = ldq_le_p(&s->w1cmask[addr]);
uint64_t oldval = ldq_le_p(&s->mmior[addr]);
+
+ uint64_t oldval_preserved = oldval & (romask | w1cmask);
+ uint64_t newval_write = val & ~romask;
+ uint64_t newval_w1c_set = val & w1cmask;
+
stq_le_p(&s->mmior[addr],
- ((oldval & romask) | (val & ~romask)) & ~(val & w1cmask));
+ (oldval_preserved | newval_write) & ~newval_w1c_set);
}
/* OR a 64-bit register with a 64-bit value */
--
MST
