Commit 187335a4 authored by Benjamin Herrenschmidt's avatar Benjamin Herrenschmidt Committed by Linus Torvalds
Browse files

[PATCH] ppc64: Detect altivec via firmware on unknown CPUs 



This patch adds detection of the Altivec capability of the CPU via the
firmware in addition to the cpu table.  This allows newer CPUs that aren't
in the table to still have working altivec support in the kernel.

It also fixes a problem where if a CPU isn't recognized as having altivec
features, and takes an altivec unavailable exception due to userland
issuing altivec instructions, the kernel would happily enable it and
context switch the registers ...  but not all of them (it would basically
forget vrsave).  With this patch, the kernel will refuse to enable altivec
when the feature isn't detected for the CPU (SIGILL).

Signed-off-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 547ee84c

arch/ppc64/kernel/head.S

+2 −0
Original line number Diff line number Diff line
@@ -922,7 +922,9 @@ fp_unavailable_common: 
altivec_unavailable_common:

	EXCEPTION_PROLOG_COMMON(0xf20, PACA_EXGEN)

#ifdef CONFIG_ALTIVEC

BEGIN_FTR_SECTION

	bne	.load_up_altivec	/* if from user, just load it up */

END_FTR_SECTION_IFSET(CPU_FTR_ALTIVEC)

#endif

	bl	.save_nvgprs

	addi	r3,r1,STACK_FRAME_OVERHEAD

arch/ppc64/kernel/prom.c

+18 −1
Original line number Diff line number Diff line
@@ -885,6 +885,7 @@ static int __init early_init_dt_scan_cpus(unsigned long node, 
					  const char *full_path, void *data)

{

	char *type = get_flat_dt_prop(node, "device_type", NULL);

	u32 *prop;



	/* We are scanning "cpu" nodes only */

	if (type == NULL || strcmp(type, "cpu") != 0)
@@ -916,6 +917,20 @@ static int __init early_init_dt_scan_cpus(unsigned long node, 
		}

	}



	/* Check if we have a VMX and eventually update CPU features */

	prop = (u32 *)get_flat_dt_prop(node, "ibm,vmx", NULL);

	if (prop && (*prop) > 0) {

		cur_cpu_spec->cpu_features |= CPU_FTR_ALTIVEC;

		cur_cpu_spec->cpu_user_features |= PPC_FEATURE_HAS_ALTIVEC;

	}



	/* Same goes for Apple's "altivec" property */

	prop = (u32 *)get_flat_dt_prop(node, "altivec", NULL);

	if (prop) {

		cur_cpu_spec->cpu_features |= CPU_FTR_ALTIVEC;

		cur_cpu_spec->cpu_user_features |= PPC_FEATURE_HAS_ALTIVEC;

	}



	return 0;

}
@@ -1104,7 +1119,9 @@ void __init early_init_devtree(void *params) 


	DBG("Scanning CPUs ...\n");



	/* Retreive hash table size from flattened tree */

	/* Retreive hash table size from flattened tree plus other

	 * CPU related informations (altivec support, boot CPU ID, ...)

	 */

	scan_flat_dt(early_init_dt_scan_cpus, NULL);



	/* If hash size wasn't obtained above, we calculate it now based on

arch/ppc64/kernel/traps.c

+0 −2
Original line number Diff line number Diff line
@@ -450,14 +450,12 @@ void kernel_fp_unavailable_exception(struct pt_regs *regs) 


void altivec_unavailable_exception(struct pt_regs *regs)

{

#ifndef CONFIG_ALTIVEC

	if (user_mode(regs)) {

		/* A user program has executed an altivec instruction,

		   but this kernel doesn't support altivec. */

		_exception(SIGILL, regs, ILL_ILLOPC, regs->nip);

		return;

	}

#endif

	printk(KERN_EMERG "Unrecoverable VMX/Altivec Unavailable Exception "

			  "%lx at %lx\n", regs->trap, regs->nip);

	die("Unrecoverable VMX/Altivec Unavailable Exception", regs, SIGABRT);

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