shithub: riscv

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pc, pc64: make sure write combining is supported in MTRR's before setting it

--- a/sys/src/9/pc/mtrr.c

+++ b/sys/src/9/pc/mtrr.c

@@ -678,6 +678,10 @@

 	if((new.type = str2type(tstr)) < 0)

 		return "bad cache type";

+	if(new.type == Writecomb

+	&& (cpu0state.cap & Capwc) == 0)

+		return "write combining not supported";

+

 	qlock(&mtrrlk);

 	newstate = cpu0state;

 	nr = getranges(&newstate, ranges, Nranges, &new);