Commit 7006b755 authored by Tom Lendacky's avatar Tom Lendacky Committed by Borislav Petkov (AMD)
Browse files

x86/sev: Allow for use of the early boot GHCB for PSC requests 



Using a GHCB for a page stage change (as opposed to the MSR protocol)
allows for multiple pages to be processed in a single request. In prep
for early PSC requests in support of unaccepted memory, update the
invocation of vmgexit_psc() to be able to use the early boot GHCB and not
just the per-CPU GHCB structure.

In order to use the proper GHCB (early boot vs per-CPU), set a flag that
indicates when the per-CPU GHCBs are available and registered. For APs,
the per-CPU GHCBs are created before they are started and registered upon
startup, so this flag can be used globally for the BSP and APs instead of
creating a per-CPU flag. This will allow for a significant reduction in
the number of MSR protocol page state change requests when accepting
memory.

Signed-off-by: default avatarTom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: default avatarBorislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/d6cbb21f87f81eb8282dd3bf6c34d9698c8a4bbc.1686063086.git.thomas.lendacky@amd.com
parent 69dcb1e3

arch/x86/kernel/sev.c

+38 −23
Original line number Diff line number Diff line
@@ -119,7 +119,19 @@ static DEFINE_PER_CPU(struct sev_es_save_area *, sev_vmsa); 


struct sev_config {

	__u64 debug		: 1,

	      __reserved	: 63;



	      /*

	       * A flag used by __set_pages_state() that indicates when the

	       * per-CPU GHCB has been created and registered and thus can be

	       * used by the BSP instead of the early boot GHCB.

	       *

	       * For APs, the per-CPU GHCB is created before they are started

	       * and registered upon startup, so this flag can be used globally

	       * for the BSP and APs.

	       */

	      ghcbs_initialized	: 1,



	      __reserved	: 62;

};



static struct sev_config sev_cfg __read_mostly;
@@ -662,7 +674,7 @@ static void pvalidate_pages(unsigned long vaddr, unsigned long npages, bool vali 
	}

}



static void __init early_set_pages_state(unsigned long paddr, unsigned long npages, enum psc_op op)

static void early_set_pages_state(unsigned long paddr, unsigned long npages, enum psc_op op)

{

	unsigned long paddr_end;

	u64 val;
@@ -756,26 +768,13 @@ void __init snp_prep_memory(unsigned long paddr, unsigned int sz, enum psc_op op 
		WARN(1, "invalid memory op %d\n", op);

}



static int vmgexit_psc(struct snp_psc_desc *desc)

static int vmgexit_psc(struct ghcb *ghcb, struct snp_psc_desc *desc)

{

	int cur_entry, end_entry, ret = 0;

	struct snp_psc_desc *data;

	struct ghcb_state state;

	struct es_em_ctxt ctxt;

	unsigned long flags;

	struct ghcb *ghcb;



	/*

	 * __sev_get_ghcb() needs to run with IRQs disabled because it is using

	 * a per-CPU GHCB.

	 */

	local_irq_save(flags);



	ghcb = __sev_get_ghcb(&state);

	if (!ghcb) {

		ret = 1;

		goto out_unlock;

	}

	vc_ghcb_invalidate(ghcb);



	/* Copy the input desc into GHCB shared buffer */

	data = (struct snp_psc_desc *)ghcb->shared_buffer;
@@ -832,20 +831,18 @@ static int vmgexit_psc(struct snp_psc_desc *desc) 
	}



out:

	__sev_put_ghcb(&state);



out_unlock:

	local_irq_restore(flags);



	return ret;

}



static void __set_pages_state(struct snp_psc_desc *data, unsigned long vaddr,

			      unsigned long vaddr_end, int op)

{

	struct ghcb_state state;

	struct psc_hdr *hdr;

	struct psc_entry *e;

	unsigned long flags;

	unsigned long pfn;

	struct ghcb *ghcb;

	int i;



	hdr = &data->hdr;
@@ -875,8 +872,20 @@ static void __set_pages_state(struct snp_psc_desc *data, unsigned long vaddr, 
		i++;

	}



	if (vmgexit_psc(data))

	local_irq_save(flags);



	if (sev_cfg.ghcbs_initialized)

		ghcb = __sev_get_ghcb(&state);

	else

		ghcb = boot_ghcb;



	if (!ghcb || vmgexit_psc(ghcb, data))

		sev_es_terminate(SEV_TERM_SET_LINUX, GHCB_TERM_PSC);



	if (sev_cfg.ghcbs_initialized)

		__sev_put_ghcb(&state);



	local_irq_restore(flags);

}



static void set_pages_state(unsigned long vaddr, unsigned long npages, int op)
@@ -884,6 +893,10 @@ static void set_pages_state(unsigned long vaddr, unsigned long npages, int op) 
	unsigned long vaddr_end, next_vaddr;

	struct snp_psc_desc desc;



	/* Use the MSR protocol when a GHCB is not available. */

	if (!boot_ghcb)

		return early_set_pages_state(__pa(vaddr), npages, op);



	vaddr = vaddr & PAGE_MASK;

	vaddr_end = vaddr + (npages << PAGE_SHIFT);
@@ -1261,6 +1274,8 @@ void setup_ghcb(void) 
		if (cc_platform_has(CC_ATTR_GUEST_SEV_SNP))

			snp_register_per_cpu_ghcb();



		sev_cfg.ghcbs_initialized = true;



		return;

	}