Commit 0459ff48 authored by Michael Kelley's avatar Michael Kelley Committed by Wei Liu
Browse files

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: default avatarMichael Kelley <mikelley@microsoft.com>
Acked-by: default avatarChristoph Hellwig <hch@lst.de>
Acked-by: default avatarBorislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/1679838727-87310-8-git-send-email-mikelley@microsoft.com


Signed-off-by: default avatarWei Liu <wei.liu@kernel.org>
parent 21eb596f

arch/x86/kernel/cpu/mshyperv.c

+1 −6
Original line number Diff line number Diff line
@@ -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) {

include/linux/swiotlb.h

+0 −2
Original line number Diff line number Diff line
@@ -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 */

kernel/dma/swiotlb.c

+1 −44
Original line number Diff line number Diff line
@@ -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;
@@ -201,34 +199,6 @@ static inline unsigned long nr_slots(u64 val) 
	return DIV_ROUND_UP(val, IO_TLB_SIZE);

}



/*

 * 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
@@ -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;