swiotlb: Remove bounce buffer remapping for Hyper-V

With changes to how Hyper-V guest VMs flip memory between private
(encrypted) and shared (decrypted), creating a second kernel virtual
mapping for shared memory is no longer necessary. Everything needed
for the transition to shared is handled by set_memory_decrypted().

As such, remove swiotlb_unencrypted_base and the associated
code.

Signed-off-by: Michael Kelley <mikelley@microsoft.com>
Acked-by: Christoph Hellwig <hch@lst.de>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/1679838727-87310-8-git-send-email-mikelley@microsoft.com
Signed-off-by: Wei Liu <wei.liu@kernel.org>

diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
index 315fc35..ac630ec 100644 (file)
--- a/arch/x86/kernel/cpu/mshyperv.c
+++ b/arch/x86/kernel/cpu/mshyperv.c
@@ -18,7 +18,6 @@
 #include <linux/kexec.h>
 #include <linux/i8253.h>
 #include <linux/random.h>
-#include <linux/swiotlb.h>
 #include <asm/processor.h>
 #include <asm/hypervisor.h>
 #include <asm/hyperv-tlfs.h>
@@ -408,12 +407,8 @@ static void __init ms_hyperv_init_platform(void)
                pr_info("Hyper-V: Isolation Config: Group A 0x%x, Group B 0x%x\n",
                        ms_hyperv.isolation_config_a, ms_hyperv.isolation_config_b);
 
-               if (hv_get_isolation_type() == HV_ISOLATION_TYPE_SNP) {
+               if (hv_get_isolation_type() == HV_ISOLATION_TYPE_SNP)
                        static_branch_enable(&isolation_type_snp);
-#ifdef CONFIG_SWIOTLB
-                       swiotlb_unencrypted_base = ms_hyperv.shared_gpa_boundary;
-#endif
-               }
        }
 
        if (hv_max_functions_eax >= HYPERV_CPUID_NESTED_FEATURES) {

diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h
index bcef10e..2ef25e6 100644 (file)
--- a/include/linux/swiotlb.h
+++ b/include/linux/swiotlb.h
@@ -180,6 +180,4 @@ static inline bool is_swiotlb_for_alloc(struct device *dev)
 }
 #endif /* CONFIG_DMA_RESTRICTED_POOL */
 
-extern phys_addr_t swiotlb_unencrypted_base;
-
 #endif /* __LINUX_SWIOTLB_H */

diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index dac42a2..0fb16bd 100644 (file)
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -73,8 +73,6 @@ static bool swiotlb_force_disable;
 
 struct io_tlb_mem io_tlb_default_mem;
 
-phys_addr_t swiotlb_unencrypted_base;
-
 static unsigned long default_nslabs = IO_TLB_DEFAULT_SIZE >> IO_TLB_SHIFT;
 static unsigned long default_nareas;
 
@@ -202,34 +200,6 @@ static inline unsigned long nr_slots(u64 val)
 }
 
 /*
- * Remap swioltb memory in the unencrypted physical address space
- * when swiotlb_unencrypted_base is set. (e.g. for Hyper-V AMD SEV-SNP
- * Isolation VMs).
- */
-#ifdef CONFIG_HAS_IOMEM
-static void *swiotlb_mem_remap(struct io_tlb_mem *mem, unsigned long bytes)
-{
-       void *vaddr = NULL;
-
-       if (swiotlb_unencrypted_base) {
-               phys_addr_t paddr = mem->start + swiotlb_unencrypted_base;
-
-               vaddr = memremap(paddr, bytes, MEMREMAP_WB);
-               if (!vaddr)
-                       pr_err("Failed to map the unencrypted memory %pa size %lx.\n",
-                              &paddr, bytes);
-       }
-
-       return vaddr;
-}
-#else
-static void *swiotlb_mem_remap(struct io_tlb_mem *mem, unsigned long bytes)
-{
-       return NULL;
-}
-#endif
-
-/*
  * Early SWIOTLB allocation may be too early to allow an architecture to
  * perform the desired operations.  This function allows the architecture to
  * call SWIOTLB when the operations are possible.  It needs to be called
@@ -238,18 +208,12 @@ static void *swiotlb_mem_remap(struct io_tlb_mem *mem, unsigned long bytes)
 void __init swiotlb_update_mem_attributes(void)
 {
        struct io_tlb_mem *mem = &io_tlb_default_mem;
-       void *vaddr;
        unsigned long bytes;
 
        if (!mem->nslabs || mem->late_alloc)
                return;
-       vaddr = phys_to_virt(mem->start);
        bytes = PAGE_ALIGN(mem->nslabs << IO_TLB_SHIFT);
-       set_memory_decrypted((unsigned long)vaddr, bytes >> PAGE_SHIFT);
-
-       mem->vaddr = swiotlb_mem_remap(mem, bytes);
-       if (!mem->vaddr)
-               mem->vaddr = vaddr;
+       set_memory_decrypted((unsigned long)mem->vaddr, bytes >> PAGE_SHIFT);
 }
 
 static void swiotlb_init_io_tlb_mem(struct io_tlb_mem *mem, phys_addr_t start,
@@ -280,13 +244,6 @@ static void swiotlb_init_io_tlb_mem(struct io_tlb_mem *mem, phys_addr_t start,
                mem->slots[i].alloc_size = 0;
        }
 
-       /*
-        * If swiotlb_unencrypted_base is set, the bounce buffer memory will
-        * be remapped and cleared in swiotlb_update_mem_attributes.
-        */
-       if (swiotlb_unencrypted_base)
-               return;
-
        memset(vaddr, 0, bytes);
        mem->vaddr = vaddr;
        return;