Messages in this thread Patch in this message | | | From | "Li, Zhen-Hua" <> | Subject | [PATCH 1/1] x86/iommu: fix incorrect bit operations in setting values | Date | Wed, 5 Nov 2014 15:30:19 +0800 |
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The function context_set_address_root() and set_root_value are setting new address in a wrong way, and this patch is trying to fix this problem.
According to Intel Vt-d specs(Feb 2011, Revision 1.3), Chapter 9.1 and 9.2, field ctp in root entry is using bits 12:63, field asr in context entry is using bits 12:63.
To set these fields, the following functions are used: static inline void context_set_address_root(struct context_entry *context, unsigned long value); and static inline void set_root_value(struct root_entry *root, unsigned long value)
But they are using an invalid method to set these fields, in current code, only a '|' operator is used to set it. This will not set the asr to the expected value if it has an old value.
For example: Before calling this function, context->lo = 0x3456789012111; value = 0x123456789abcef12;
After we call context_set_address_root(context, value), expected result is context->lo == 0x123456789abce111;
But the actual result is: context->lo == 0x1237577f9bbde111;
So we need to clear bits 12:63 before setting the new value, this will fix this problem.
Signed-off-by: Li, Zhen-Hua <zhen-hual@hp.com> --- drivers/iommu/intel-iommu.c | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c index a27d6cb..11ac47b 100644 --- a/drivers/iommu/intel-iommu.c +++ b/drivers/iommu/intel-iommu.c @@ -195,6 +195,7 @@ static inline void set_root_present(struct root_entry *root) } static inline void set_root_value(struct root_entry *root, unsigned long value) { + root->val &= ~VTD_PAGE_MASK; root->val |= value & VTD_PAGE_MASK; } @@ -247,6 +248,7 @@ static inline void context_set_translation_type(struct context_entry *context, static inline void context_set_address_root(struct context_entry *context, unsigned long value) { + context->lo &= ~VTD_PAGE_MASK; context->lo |= value & VTD_PAGE_MASK; } -- 2.0.0-rc0
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